1. Field of the Invention
The present invention relates to a hybrid material for use as raw materials for cosmetics and a method of preparation thereof. More specifically, it relates to a hybrid material for raw materials for cosmetics showing good safety, low toxicity, low irritation, good sustained release, good dispersibility, etc., and a method of preparation thereof.
2. Description of the Related Art
Human skin includes two layers, the epidermis and dermis. The epidermis consists of Keratinocytes which are keratin-forming cells, Melanocytes which are melanin-containing cells, and Langerhans which are cells related to immune function in the epidermis. The dermis has collagen which is an extra-cellular matrix (ECM) component, and fibroblast forming glycosaminoglycans (GAGs). These components must maintain their functions to keep human skin healthy and beautiful. However, as humans get older or their skin exposed to harmful environments such as ultraviolet lays, the concentration of reactive oxygen species (ROS) increases to accelerate oxidation, thereby resulting in phenomena such as pigmentary deposit, keratinization and wrinkles.
Thus, there have been various efforts to prevent or inhibit natural aging or temporary skin troubles occurring in skin. As part thereof, various natural and synthetic materials have been developed and used as raw materials for cosmetics for skin care. Such raw materials for cosmetics may be classified in terms of their functions into anti-oxidant, keratin remover, skin whitening agent, spot/freckle remover, skin calmative, skin moisturizing agent, skin activator, fire blight preventing agent, skin metabolism promoter, wrinkle preventing agent, etc.
Vitamins can be mentioned as one of most representative raw materials for cosmetics. Vitamins are essential materials for the body, having functions such as promoting body metabolism, anti-oxidation, protecting cell wall, enhancing immunity, increasing resistance to infection, etc. For human beings, biosynthesis of vitamins is impossible and thus intake of vitamins through food is essential. When vitamins are deficient, various diseases occur. In addition, vitamins play an important part in skin care and treatment such as preventing pigmentary deposit, promoting synthesis of collagen, blocking ultraviolet rays, preventing drying and keratinization of skin, preventing wrinkles and moisturizing skin. Exemplary vitamins include vitamin A such as retinol, vitamin C such as ascorbic acid, vitamin E such as tocopherol, and derivatives thereof.
In addition to vitamins, important raw materials for cosmetics include α-hydroxy acid (AHA) such as lactic acid, citric acid and salicylic acid, which functions to remove keratin layer of skin and thereby accelerate metabolism of skin; kojic acid (5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-on) which functions to whiten skin by inhibiting melanin biosynthesis; indol-3-acetic acid (C10H9NO2) which functions to prevent wrinkles by accelerating fibroblast multiplication; salicylic acid (2-hydroxy benzoic acid; C7H6O3) which functions as an anti-oxidant to treat pimples; and other various known raw materials for cosmetics.
However, most of the aforementioned raw materials for cosmetics are limited in practical use because of problems in their inherent stability, skin irritation and toxicity, sustained release, dispersibility, etc., and thus have not exerted their functions and effects sufficiently. For example, vitamins are very unstable physicochemically and easily destroyed by heat, light, moisture, oxygen, alkali, etc., leading to deterioration of their functions and effects, or discoloration or malodor. Also, α-hydroxy acid such as lactic acid irritates skin. Kojic acid degenerates melanin pigments and melanin cells by penetrating into skin base layer, and thus if used in high concentration, induces various skin diseases such as dermatitis and skin cancer. It is also oxidized under light and high temperature to cause discoloration. Furthermore, indol-3-acetic acid is unstable under external environment, heat, light, moisture, oxygen, etc., especially light, to cause discoloration and malodor.
There have been many studies on formulation technologies to stabilize raw materials for cosmetics or reduce skin irritation or toxicity. In particular, such studies have been performed for vitamins, and based on them, studies on materials other than vitamins have been done.
Major prior stabilization methods for vitamins include oil-in-water (O/W) or water-in-oil (W/O) emulsion technology, multiple liquid crystal film technology, liposome technology, porous bead technology, water-soluble polymer technology and polysaccharide capsule technology.
Korean Patent No. 115706 discloses a method for preparing a vitamin nano-capsule by impregnating and sealing vitamin and various active components within an inner phase fine globule, and further stabilizing this using a double-layer lipid film. Furthermore, Korean Patent Laid-open Publication No. 2000-0048451 discloses a method for capsuling a lipophilic active component globule core with water insoluble synthetic or natural water-dispersible anionic polymers. Korean Patent Laid-open Publication No. 2000-0069893 discloses a method for stabilization by impregnating an active component in polysaccharide globule such as starch followed by coating the exterior with water-soluble polymers, or a method for stabilization by micro-emulsifying the active component and stabilizing the exterior using an anionic, non-ionic, cationic or amphionic surfactant.
Korean Patent No. 202401 discloses a method wherein an active component is impregnated in a polysaccharide and the exterior is capsuled with a neutral liquid crystal. Korean Patent No. 236484 discloses a method wherein a stable emulsion containing a water-soluble active component is formed and the exterior is further stabilized with a gelatin capsule. Korean Patent Laid-open Publication No. 1999-0070885 discloses a method wherein a mixture of vitamins such as water-soluble vitamins and fat-soluble vitamins is mixed with solid powder such as mica thereby absorbing into the powder and the surface thereof is coated with highly viscous liquid oil. Korean Patent No. 222000 discloses a stabilization method by applying simultaneously a liposome technology and a technology for forming liquid crystal. Korean Patent Laid-open Publication No. 2001-0002411 discloses a stabilization method by combination with natural materials such as coffee beans, tea leaves and cacao extracts.
Methods of using more stable derivative have been reported, but it has some problems. For example, magnesium ascorbyl phosphate can be easily converted into a form of biocompatible L-ascorbic acid compared to other derivatives, but it is difficult to be absorbed into skin. Ascorbyl palmitate is easily absorbed into skin, but difficult to be converted into a form of L-ascorbic acid.
Technologies for stabilizing vitamin A include oil-in-water or water-in-oil emulsion formulation technologies using an oil-soluble anti-oxidant such as butylated hydroxytoluene (BHT) or butylated hydroxy anisole (BHA), a water-soluble anti-oxidant such as ascorbic acid, or a chelating agent such as α-tocopherol. See Korean Patent Laid-open Publication Nos. 1990-021511 and 1999-0018726; U.S. Pat. Nos. 4,247,547; 4,826,828; 4,720,353; and 4,466,805; and EP 0 440 398 B1.
Japanese Patent Laid-open Publication No. Hei 2-83309 discloses a technology wherein a water-soluble L-ascorbic acid derivative is introduced into the inner phase of a water-in-oil emulsion to protect from oxidation or decomposition. Japanese Patent Laid-open Publication No. Sho 55-64511 discloses a technology wherein higher fatty acid esters are included within cyclodextrine. Japanese Patent Laid-open Publication No. Hei 3-5326 discloses a technology wherein L-ascorbic acid phosphoric acid esters or sulfuric acid esters are added to liposome to improve storage stability. Japanese Patent Laid-open Publication No. Hei 5-345714 discloses a technology wherein L-ascorbic acid esters are combined with certain water-soluble polymers to improve stability. All of these patent publications disclose using ester derivatives of L-ascorbic acid, which improves stability compared to L-ascorbic acid itself, but are known to be less effective in reducing melanin or inhibiting tyrosinase activities.
Korean Patent Laid-open Publication No. 2000-0026158 discloses a stabilization method using an oil-in-water emulsion which encapsulate retinol or derivatives based on a matrix of collagen and chitosan. However, retinol or derivatives are known to be thermodynamically very unstable. In particular, they are easily oxidized by oxygen in air, light and heat, resulting in loss of their effects and causing irritation to skin by decomposed retinol derivatives. BHA or BHT of the prior art may be added to stabilize retinol derivatives and reduce discoloration, but these components are also irritant to skin and recently avoided. There have been recent developments proposed on a number of methods for encapsuling with gelatin, alginic acid, etc., but these methods cause excess retinol to burst out at once and irritate skin.
The following methods are known. A method of microcapsuling tocopherol contained in the inner phase of retinyl palmitate, a fat-soluble active component with film material of crosslinked collagen and glucoseaminogrucane (Korean Patent Laid-open Publication No. 1999-0065437); a method of using double-capsuling consisting of first encapsuling an inner phase of retinol and secondly capsuling with gellane gum (Korean Patent Laid-open Publication No. 1998-21511); a method of capsuling in liposome (Korean Patent Laid-open Publication No. 1998-703668); a method of stabilizing retinyl palmitate in liquid crystal gel phase (Korean Patent Laid-open Publication No. 1996-033439). Additionally, a number of multi-emulsified forms, particularly W/O/W were also proposed to improve shortcomings of the prior single-emulsified forms such as W/O or O/W: see, U.S. Pat. No. 3,399,263, Great Britain Patent No. 1235667, Japanese Patent Laid-open Publication No. Sho 52-134029, Japanese Patent Laid-open Publication No. Sho 53-31578, Japanese Patent Laid-open Publication No. Sho 57-15829, Japanese Patent Laid-open Publication No. Sho 58-183611, Japanese Patent Laid-open Publication No. Sho 59-80326, Japanese Patent Laid-open Publication No. Sho 59-127646, Japanese Patent Laid-open Publication No. Sho 62-2561, Japanese Patent Laid-open Publication No. Sho 63-33311, Korean Patent Laid-open Publication No. 1995-0000131. There were also known methods wherein an active component is included in pores of porous microbeads in a similar manner to microcapsule (U.S. Pat. No. 5,145,675); and a method wherein the surface of porous microbeads containing an active component is treated with silicone or derivatives thereof (Korean Patent Laid-open Publication No. 2000-0067126).
As described above, the prior methods for stabilizing vitamins basically comprises combining a water-soluble or fat-soluble vitamin with oily or water phase polymers, surfactants and other organics thereby forming an inner phase, and if necessary, further encapsuling the exterior with polymers, surfactants, polysaccharides, oils, etc., although slightly different in specific matters.
In the case of α-hydroxy acid (AHA) such as lactic acid, citric acid and salicylic acid, there is no stability problem in using them as active components as raw materials for cosmetics, but if released in excess and applied to skin, they cause severe skin irritation such as torrid heat feeling and prickling. Thus, the amounts must be controlled when used as raw materials for cosmetics.
For kojic acid, Korean Patent Laid-open Publication No. 1998-044041 discloses a technology for preventing low molecular weight kojic acid from penetrating into skin, wherein a kojic acid is converted to a higher molecular weight by e.g. polymerizing the kojic acid using a kojic acid/amino acid complex. Furthermore, Korean Patent Laid-open Publication No. 2002-0025356 discloses a method for solving the problems of potency reduction and browning due to oxidation of kojic acid, using a kojic acid/amino acid complex and concentrated green tea extracts having the anti-oxidation effects. U.S. Pat. No. 4,847,074 discloses a technology for preventing browning and improving stability by including kojic acid within cyclodextrine. Furthermore, U.S. Pat. No. 4,369,174 discloses a method for improving stability against heat and light using derivatives obtained from the esterification reaction of kojic acid and aliphatic carboxylic acid.
In the case of indol-3-acetic acid, since its amount in a formulation is extremely small e.g. about 300 ppm, almost no separate report has been made on a stabilization method. Thus, prior stabilization methods for vitamins are mostly used for it. One prior art for indol-3-acetic acid is Korean Patent Application No. 2001-45629 which discloses a method for using it as a raw material for cosmetics by stabilizing it in the form of liposome.
The prior arts as described above have their own characteristics in degree of stabilization of each active component, release, delivery, biocompatibility, convenience, cost, and the like. However, there still remains a need for further improvements in safety, stability, sustained release, cost, and the like.